U.S. Pat. No. 4,279,958 discloses a composite panel wherein a non-woven rayon mat (3,21) is disposed between a layer of fibrous glass board and a layer of foamed-in-place urethane foam. While the non-woven mat limits penetration of the foam into the fibrous glass board, it nevertheless permits penetration of more foam into the board than is necessary to establish a good bond.